Methods and apparatus for dynamically assigning time slots in a wireless communication system

ABSTRACT

A wireless communication system having a base unit and a plurality of remote transceiver units utilizes a dynamic time slot assignment scheme for channel access. The base unit receives and processes a channel access request message from a remote transceiver unit and prepares a channel measurement request message in response. If an M th  time slot of a time frame is available, the base unit sends this message in the M th  time slot and receives a message having channel measurement data in the M th  time slot of the next time frame. On the other hand, if the M th  time slot of the time frame is already reserved, the base unit sends the message in an N th  time slot of the time frame and receives a message having the channel measurement data in the N th  time slot of the next time frame. The base unit selects, based on the channel measurement data, an appropriate channel for communication for the remote transceiver unit. Continuing with use of the dynamic slot assignment, the base unit sends a message having a channel identifier associated with the selected channel and receives an acknowledgement from the remote transceiver unit in response.

RELATED APPLICATIONS

This application is a continuation of prior U.S. patent application Ser.No. 09/597,044 filed on Jun. 20, 2000, now U.S. Pat. No. 6,801,513issued on Oct. 5, 2004, which claims the benefit of U.S. ProvisionalApplication No. 60/140,959, filed Jun. 23, 1999 and entitled “Method forEstablishing a Communication Channel in a Personal Wireless AccessNetwork,” which is incorporated herein in its entirety.

The following applications, assigned to the Assignee of the currentinvention, and being filed concurrently, contain material related to thesubject matter of this application, and are incorporated herein byreference:

D. Gibbons et al., entitled “Establishing a Communication Channel in aWireless Network,” U.S. Ser. No. 09/597,043, filed Jun. 20, 2000; and

by L. Hong et al., entitled “Polling Methods for Use in a WirelessCommunication System,” U.S. Ser. No. 09/597,016, filed Jun. 20, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to wireless communicationsystems utilizing time division multiple access (TDMA) techniques, andmore particularly to the assignment of time slots in a dynamic fashionin such communication systems.

2. Description of the Related Art

In cellular telephone systems, methods for assigning time slots in adynamic fashion are known. These methods exist, for example, in GlobalSystems for Mobile (GSM) communication systems. Such systems definemultiple time slots, each of which may be uniquely assigned to a mobileunit for communication. Here, one of the time slots that is not alreadyin use is selected for temporary use in a communication between base andmobile units, another one of the time slots is selected subsequently,and so on. Other systems, such as “fixed wireless systems,” however, areinherently different from cellular telephone systems. What is needed arealternative methods of dynamically assigning time slots which aresuitable to other systems, such as fixed wireless systems.

SUMMARY OF THE INVENTION

Methods and apparatus for dynamically assigning time slots in a wirelesscommunication system are described. One method includes the initialsteps of receiving, at a base unit, a first message from a remotetransceiver unit; and processing the first message and generating asecond message in response. The method includes the further steps of,when an M^(th) time slot of a time frame is available, sending, from thebase unit to the remote transceiver unit, the second message that isresponsive to the first message in the M^(th) time slot; and receiving,at the base unit from the remote transceiver unit, a third message thatis responsive to the second message in the M^(th) time slot of afollowing time frame. The method includes the further steps of, when theM^(th) time slot of the time frame is unavailable, sending, from thebase unit to the remote transceiver unit, the second message that isresponsive to the first message in an N^(th) time slot of the timeframe, where the N^(th) time slot follows the M^(th) time slot in thetime frame; and receiving, at the base unit from the remote transceiverunit, the third message that is responsive to the second message in theN^(th) time slot of the following time frame.

If both the M^(th) and N^(th) time slots are unavailable, the base unitmay assign other subsequent time slots in the time frame in a similarfashion (e.g., P^(th) or Q^(th) time slots). The dynamic slot assignmentis advantageously applied to a call establishment scheme, where thefirst message is a channel access request message, the second message isa channel measurement request message, and the third message is achannel measurement data message. The base unit selects a channel forcommunication based on the channel measurement data and, continuing withthe dynamic slot assignment, sends a message having a channel identifierassociated with the selected channel and receives an acknowledgementfrom the remote transceiver unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a wireless communication system which mayembody the present invention, the wireless communication systemincluding at least one base unit and a plurality of transceiver units;

FIG. 2 is an illustration of software components which are suitable foruse in implementing the inventive methods described herein;

FIG. 3 is an illustrative representation of protocol layers utilized inthe base unit and transceiver units;

FIG. 4 is an illustrative representation of a Medium Access Channel(MAC) layer utilized in the base unit and transceiver units;

FIG. 5 is a process diagram which describes a method for dynamicallyassigning time slots in the wireless communication system of FIG. 1; and

FIG. 6 is a flowchart describing a method for dynamically assigning timeslots in the wireless communication system of FIG. 1.

FIGS. 7A, 7B, and 7C depict the structures of an unsolicited CACmessage, a solicited CAC message, and an installation CAC message,respectively, in accordance with one embodiment of the presentinvention.

FIG. 8 depicts a network access channel and broadcast frame structure inaccordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Methods and apparatus for dynamically assigning time slots in a wirelesscommunication system are described. A base unit receives a message froma transceiver unit and generates a message in response. The base unitidentifies the next available and unreserved time slot “M” of a timeframe having L time slots, and reserves it for communication with thetransceiver unit. The base unit sends the response message in the M^(th)time slot of the time frame, and receives a message from the transceiverunit in the M^(th) time slot of the next time frame in a predeterminedfashion. Thereafter, the base unit unreserves the M^(th) time slot forsubsequent use in connection with that or another transceiver unit. Theprocess repeats, where “M” may be a different number in each pass. Whenapplied in a call establishment procedure, the process repeats until atraffic channel is assigned for communications. The method is performedsubstantially simultaneously at the base unit for each one of multipletransceiver units.

FIG. 1 is an illustrative representation of a wireless communicationsystem 100 which utilizes time division multiple access (TDMA) orTDMA-like communication methodologies. Wireless communication system 100includes at least one base unit 106 having one or more antennas 108, anda plurality of remote units 102 (“RUs” or “receiver units”), such asremote unit 104. Base unit 106 and remote units 102 communicate viaradio frequency (RF) signals, such as RF signals 110 between base unit106 and remote unit 104. Wireless communication system 100 can make useof a number of additional different communication techniques, such asfrequency division multiplexing (FDM) or orthogonal frequency divisionmultiplexing (OFDM). Preferably, wireless communication system 100 is afixed wireless system (FWS), where base unit 106 provides telephone andhigh-speed data communication to each one of a number of fixed-locationsubscribers equipped with an RU. In addition, wireless communicationsystem 100 is referred to as a Personal Communication System (PCS)Wireless Access Network (PWAN).

Referring to FIG. 2, the methods described herein may be embodied andimplemented in transceiver unit 104 and base unit 106 of FIG. 1 (as wellas other transceiver and base units) in connection with software usingsoftware components 200 shown in FIG. 2. The software may be embedded inor stored on a disk 202 or memory 204, executable on a computer 206 or aprocessor 208. Thus, the inventive features may exist in asignal-bearing medium which embodies a program of machine-readableinstructions executable by a processing apparatus which perform themethods.

FIG. 3 is an illustration of a layered architecture 300 utilized inwireless communication system 100 of FIG. 1. The layering principles ofthe Reference Model for Open System Interconnection (OSI) as containedin International Telegraph and Telephone Consultative Committee (CCITT)recommendations X.200 and X.210 are well-known in the art. Layeredarchitecture 300 includes an applications layer 302 (or Layer 4), anetwork layer 304 (or Layer 3), a data link layer 312 (or Layer 2), anda physical layer 310 (or Layer 1). Data link layer 312 of the PWANconsists of two sublayers, the data link control (DLC) 306 and themedium access control (MAC) 308. Each sublayer is defined independentlyand interfaces to adjacent layers through a set of primitives andservice access points (SAPs). The layering principles of the ReferenceModel for Open System Interconnection (OSI) as contained inInternational Telegraph and Telephone Consultative Committee (CCITT)recommendations X.200 and X.210 are well-known in the art.

MAC 308 interfaces to adjacent layers by the use of protocol primitives.MAC 308 interfaces with DLC 306, which resides above MAC 308. MAC 308also interfaces with the “airlink” physical layer 310, which residesbelow MAC 308. In addition, MAC 308 provides interfaces to a local RadioManagement Entity (RME) and to a broadcast control application (both notshown in FIG. 3). MAC 308 provides an orderly and efficient use ofphysical layer 310 to DLC 306. Two services are provided by MAC 308:access control service and link control service.

The access control service provides a mechanism for DLC 306 to set upphysical channels from either base unit 106 or transceiver unit 104. MAC308 is responsible for the attachment of a cyclic redundancy check (CRC)checksum to access control messages prior to submittal to physical layer310. The CRC is checked on the receiving end to detect errors intransmission. The link control service provides physical layer access tomessages submitted from DLC 306 for link control functions. Further,link control service provides a prioritized data delivery service, aswell as segmentation and reassembly of long messages. Link controlservice handles a CRC-16 checksum for link control messages prior tosubmittal to or reception from physical layer 310.

Broadcast service provides a means for the applications to access thebroadcast medium. In base unit 106, this service is required fortransmitting broadcast messages; in transceiver unit 104, this serviceis required for receiving broadcast messages. Physical layer 310 is thelowest layer in the OSI Reference Model and it supports all functionsfor the transmission of bit streams on the physical medium. These bitstreams are transferred on traffic and control channels. The followingare some of the services required by physical layer 310: (1) the abilityto generate a physical airlink connection (simplex or full duplex) forthe transmission of bits in the same order in which they are submittedto physical layer 310; and (2) a broadcast capability between base unit106 and multiple tranceiver units.

FIG. 4 is an illustration of an internal architecture of MAC 308 of FIG.3. Internal MAC entities include a broadcast control entity 402, anaccess control entity 404, and a link control entity 408. SAPs providecommunication channels to other layers in the system. Broadcast controlentity 402 provides a broadcast service from base unit 106 totransceiver units. It communicates with an associated application viathe B-SAP, and with physical layer 310 via the BR-SAR. Access controlentity 404 provides the functions necessary to gain access to thephysical layer services. It communicates with DLC 306 via an AC-SAP.Access control entity 404 communicates with physical layer 310 via acommon access SAP (CA-SAP) and a common link SAP (CL-SAP). Finally, linkcontrol entity 408 accepts service requests for data transferred fromDLC 306 and performs the necessary transformations to submit theinformation to physical layer 310. This link control entity 408 utilizesthe services of segmentation for its messages at the DSP physical layer.

The access control mechanism provides base unit 106 and its constituenttransceiver units 102 with a mechanism to communicate prior to the setupof a connection-oriented datalink for the purposes of, among otherthings, setup of a connection-oriented traffic and associated data linkchannel. The access control mechanism uses Common Access channel (CAC)and Common Link channel (CLC) for this communication. The physical layerprovides the following CAC/CLC channels/code keys per subband pair foruse by access control: (1) one CLC channel with one code key; and (2)two CAC channels with two code keys each. Transceiver units are assignedto a particular subband pair and CAC channel in the start-up procedure.

Messages transmitted over the CAC channel can be sent in either asolicited (S-CAC) or unsolicited (U-CAC) fashion. With respect tounsolicited CAC transmissions, when transceiver unit 104 initiates acall (i.e., originating call), it utilizes an unsolicited transmissionapproach. Here, transceiver unit 104 transmits a CAC message in thefirst available time slot and does not wait to be scheduled. SlottedALOHA access scheme is used for U-CAC transmissions. If the unsolicitedCAC transmission is not acknowledged by base unit 106 via the CLC insome given period of time (t_mac-access), then transceiver unit 104waits a random period of time (t_mac-AccessBackoff) before re-trying theunsolicited CAC transmission. This process will continue up to aprovisionable number of times (n_mac-access).

With respect to solicited CAC or S-CAC transmissions, after the initialaccess to the system, transceiver unit 104 uses a scheduled CAC channelfor the remainder of a call establishment procedure in a predefineddynamic slot assignment scheme, which is described below. Transceiverunit 104 is guaranteed a collision-free transmission on the CAC at thistime. Since transceiver unit 104 ID is dynamically assigned, certainmessages exchanging during start-up have to use a transceiver unitHardware Serial Number (HSN) as an identifier.

As described above, the CAC and CLC messages that are used fortransceiver unit access to the PWAN use a DSA-TDMA scheme to access themedium. Each CAC or CLC message is transmitted in one 3 millisecond timeslot of a 12 millisecond frame (four time slots per time frame). Slotsare counted in a relative sense at both base unit 106 and transceiverunit 104 and are assigned dynamically throughout the call establishmentprocedure. Base unit 106 and transceiver unit 104 maintain a slot countfrom one to N (n-mac-dsaslots), where N (n-mac-dsaslots) is aprovisionable value that is the same at both base unit 106 andtransceiver unit 104. At any given time, the current value of the slotcount may not necessarily be equal at base unit 106 and transceiver unit104.

FIG. 5 is a process diagram which describes a method for dynamicallyassigning slots in a communication system. More particularly, FIG. 5illustrates the DSA-TDMA procedure for an originating call messagesequence. The inventive method or procedure in which the slot resourcesare managed at base unit 106 and transceiver unit 104 to accomplish thesolicited messaging is what is emphasized in the following description.

Transceiver unit 104 is required to originate a connection and thereforetransmits an ACCESS message using the UCAC channel in the firstavailable slot (step 502 or [1]). The retry mechanism is of a slottedALOHA nature. In the example shown, the first available slot isTransceiver Slot #2. The message sent from transceiver unit 104 at step502 may be referred to as a “channel access request message” or a “callestablishment request message” (e.g., for a telephone or voice call).MAC access manager of base unit 106 receives the ACCESS message in theform of a cac-data.ind primitive (step 504 or [2]).

The MAC will process this message and, if bandwidth in the cell isavailable, reply to the accessing transceiver unit 104 with a CONNECTmessage via the CLC channel. The CONNECT message is delivered to the MACslot control mechanism via a clc-data.req primitive. The MAC slotcontrol entity transmits the CONNECT message in the next available timeslot, which in this case is Base Slot #2. The MAC slot control entity inbase unit 106 then starts a watchdog timer (T₁) associated with BaseSlot #2. If a solicited CAC message is not received in this time slotwithin this time, the MAC slot control entity “frees” the slot. Themessage sent from base unit 106 here may be referred to as a “channelmeasurement request message.” This message is a request to transceiverunit 104 to measure a plurality of traffic channels in the system forsubsequent selection of the single best channel to use forcommunication.

The MAC slot control entity of transceiver unit 104 receives the CONNECTin Transceiver Slot #4, and delivers the CONNECT to the MAC accessmanager of transceiver unit 104 via a clc-data.ind tagged withTransceiver Slot #4 (step 506 or [3]). The MAC access manager oftransceiver unit 104 processes the CONNECT message and submits aCONNECT-ACK message via a cac-data.req primitive to the MAC slot controlentity. The MAC access manager tags this primitive with Transceiver Slot#4, representing the slot in which the associated CONNECT message wasreceived. Note that Transceiver Slot #4 is not used by the MAC accessmanager of transceiver unit 104. As an example of a busy condition, asecond simultaneous link establishment may occur with the same orperhaps a second transceiver unit utilizing Base Slot #4 (step 508 or[4]). Base Slot #4 is now busy and reserved.

The MAC slot control entity of transceiver unit 104 receives thecac-data.req primitive containing the CONNECT-ACK message (step 510 or[5]). This message will be transmitted using the solicited CAC (s-cac)key in Transceiver Slot #4. As apparent in FIG. 5, for each “cycle” orpair of consecutive time frames, messages are received and sent in thesame time slot. This implies that the MAC slot control entity needs todefer the message until Transceiver Slot #4 becomes available; this isan inherent delay in this solicited TDMA approach. The message sent atstep 510 may be referred to as a “channel measurement data message”since, in response to the previous message from base unit 106,transceiver unit 104 measured a number of different traffic channels andplaced measurement data in the channel measurement data message.

The MAC slot control entity of base unit 106 receives the CONNECT-ACKmessage during Base Slot #2, as expected (step 512 or [6]). The MAC slotcontrol entity of base unit 106 frees up Base Slot #2 as a resource thatmay be used by other Base MAC access managers, and then resets anddisables the watchdog timer T₁. The CONNECT-ACK message is processed.The channel measurement data in the message is used by base unit 106 toselect one of the plurality of traffic channels for communication.

The MAC access manager of base unit 106 continues to process theCONNECT-ACK message, responding with a DELAY message and submitting thismessage via a clc-data.req primitive to the MAC slot control entity ofbase unit 106 during Base Slot #3 (step 514 or [7]). The MAC slotcontrol entity of base unit 106 waits until the next available slot totransmit this message over the CLC channel. In this case, the nextavailable slot is Base Slot #1, since Base Slot #4 is busy with a secondcall establishment. The message is transmitted in Base Slot #1 andwatchdog timer T₁ is again enabled. This message contains a channelidentifier uniquely associated with the selected channel forcommunication.

The MAC slot control entity of transceiver unit 104 receives the DELAYmessage during Transceiver Slot #3 (step 516 or [8]). The DELAY messageis delivered to the MAC access manager of transceiver unit 104 andtagged with Transceiver Slot #3. The MAC access manager of transceiverunit 104 processes this message and responds with a DELAY.ACK messagewhich is delivered in a cacdata.req primitive. The MAC slot controlentity then waits for Transceiver Slot #3 and transmits the DELAY-ACKmessage. The cac-data.ind arrives at base unit 106 during Base Slot #1as expected (step 518 or [9]). The MAC slot control entity of base unit106 will free Base Slot #1 as a resource that may be used for other BaseMAC access managers and resets and disables the watchdog timer T₁. Thismessage may be referred to as an acknowledgement message fromtransceiver unit 104.

Reviewing the call process diagram of FIG. 5, the first message sentfrom transceiver unit 104 at step 502 may be a channel access requestmessage or a call establishment request message, the second message sentfrom base unit 106 at step 504 may be a channel measurement requestmessage, the third message sent from transceiver unit 104 at step 510may be a channel measurement data message, the fourth message sent frombase unit 106 at step 514 may be a channel identification message, andthe fifth message sent from transceiver unit 104 at step 518 may be anacknowledgement message. When transceiver unit 104 receives the selectedand assigned traffic channel, it performs conventional synchronizationand training on that traffic channel. Thereafter, transceiver and baseunits 104 and 106 communicate over the selected traffic channel untiltermination. The traffic channel may be a voice traffic channel for atelephone call, or a data traffic channel for communicating high speeddata such as Internet data.

FIG. 6 is a flowchart describing more generally the method fordynamically assigning time slots in wireless communication system 100 ofFIG. 1. Beginning at a start block 600, base unit 106 receives a messagefrom transceiver unit 104 (step 602). Base unit 106 processes thismessage and generates a message in response (step 604). Next, base unit106 identifies the next time slot “M” (of a time frame having L timeslots) that is available and unreserved (step 606), and reserves it forcommunication with transceiver unit 104 (step 608). As an example, theMth available time slot may be the 1^(st) time slot, the 2^(nd) timeslot, the 3^(rd) time slot, or the 4^(th) time slot of a time framehaving four time slots. Base unit 106 sends the response message in theM^(th) time slot of a time frame (step 610). Before a predetermined timeperiod expires, base unit 106 receives a message from transceiver unit104 in the M^(th) time slot of the next time frame (step 612), asexpected. This message is responsive to the message sent by base unit106 in step 610. Thereafter, base unit 106 unreserves the time slot forsubsequent use in connection with transceiver unit 104 or anothertransceiver unit (step 614). This process repeats starting again at step604, where M may be different for each pass in step 606. When applied ina call establishment procedure, the process repeats until a trafficchannel is assigned for communications. The method is performedsubstantially simultaneously at base unit 106 for each one of multipletransceiver units desiring access.

Thus, methods for dynamically assigning time slots between a base unitand a transceiver unit of a wireless communication system defining Ltime slots per time frame have been described. In one method, theinitial steps include receiving, at a base unit, a first message; andprocessing the first message and generating a second message inresponse. The method includes the further steps of, when an M^(th) timeslot of a time frame is available, sending, from the base unit, thesecond message that is responsive to the first message in the M^(th)time slot; and receiving, at the base unit, a third message that isresponsive to the second message in the M^(th) time slot of a followingtime frame. The method includes the further steps of, when the M^(th)time slot of the time frame is unavailable, sending, from the base unit,the second message that is responsive to the first message in an N^(th)time slot of the time frame, the N^(th) time slot following the M^(th)time slot in the time frame; and receiving, at the base unit, the thirdmessage that is responsive to the second message in the N^(th) time slotof the following time frame.

The method may include the further steps of, when the M^(th) time slotof the time frame is available, reserving the M^(th) time slot of thefollowing time frame prior to receiving the third message; andunreserving the M^(th) time slot for after receiving the third messagein the M^(th) time slot of the following time frame. Similarly, themethod may include the further steps of, when the M^(th) time slot ofthe time frame is unavailable, reserving the N^(th) time slot of thefollowing time frame prior to receiving the third message; andunreserving the N^(th) time slot after receiving the third message inthe N^(th) time slot of the following time frame. In a callestablishment procedure, the first message may be a channel accessrequest for communication, the second message may be a channelmeasurement request, and the third message may include channelmeasurement data.

Another method for dynamically assigning time slots in wirelesscommunication system includes the steps of identifying a next availabletime slot M of a time frame having L time slots; reserving the M^(th)time slot of the time frame; sending a first message in the M^(th) timeslot of the time frame; receiving a second message that is responsive tothe first message in an M^(th) time slot of a following time frame; andunreserving the M^(th) time slot for subsequent use.

FIGS. 7A, 7B, and 7C depict the structures of an unsolicited CACmessage, a solicited CAC message, and an installation CAC message,respectively, in accordance with one embodiment of the presentinvention. These figures show the assignment of each bit of the 9 octetsof the CAC messages. In these figures, the “RU Access ID” is theidentified used by the remote unit (RU) to distinguish sessions, the“Base Access ID” is the identified used by the Base to distinguishsessions, the “BSOC” is the base station offset code, the “Message ID”is the message identifier whose contents is in the payload field, the“Subband” is the subband in which the RU is operating, the “Seq Number”is the identifier of a segmented message, “M” is the “more” bit, where a0/1 indicates none/more to follow, the “RU ID” identifies the RU ofinterest, the “HSN” is the hardware serial number, and the “Payload” isthe CAC message payload, including up to 5 bytes for UCAC, 7 bytes forSCAC, and 3 bytes for an installation CAC.

FIG. 8 depicts a network access channel and broadcast frame structure inaccordance with a preferred embodiment of the present invention. Asshown in FIG. 8, each network access channel (NAC) slot occupies fourconsecutive time-slots over 1.5 ms and contains a single NAC message. ANAC frame consists of five NAC slots occupying the second half of eachof five TDMA frames over 15 ms. The five NAC slots in each NAC frame arecomprised of one BRC/UCAC slot and four CLC/SCAC slots.

Each base is assigned an offset code (BSOC ) to create a time reusepattern of 32. A broadcast slot (BC slot) is defined as being one NACframe in duration. Each Base, Bn, transmits a single broadcast messagein its assigned BC slot. The cycle consisting of 32 BC slots is definedas a Broadcast Frame (BC Frame). The BC Frame has duration 32×15 ms=480ms. Thus each Base transmits one broadcast message every BC frame. TheBC message cycle requires eight broadcast messages for each base, thusrequiring the definition of the broadcast super frame. A broadcast superframe consists of eight broadcast slots (256 BC Frames) occupying aduration of 8*32*15* ms=3840 ms. Each Phase of the BC super frame inFIG. 8 is designated with a letter from A to H.

It should be readily apparent and understood that the foregoingdescription is only illustrative of the invention and in particularprovides preferred embodiments thereof. Various alternatives andmodifications can be devised by those skilled in the art withoutdeparting from the true spirit and scope of the invention. Accordingly,the present invention is intended to embrace all such alternatives,modifications, and variations which fall within the scope of theappended claims.

1. A computer memory having computer instructions embedded thereon fordynamically assigning time slots between a base unit and a transceiverunit of a wireless communication system having a predetermined number oftime slots per time frame, the computer readable medium comprisinginstructions that cause one or more computers to: receive a firstmessage; process the first message and generate a second message inresponse thereto; when a first selected time slot of a time frame isavailable: send the second message that is responsive to the firstmessage in the first time slot; receive a third message that isresponsive to the second message in the first time slot of a subsequenttime frame; when the first time slot of the time frame is unavailable:send the second message that is responsive to the first message in asecond time slot of the time frame, the second time slot being differentfrom the first time slot in the time frame; and receive the thirdmessage that is responsive to the second message in the second time slotof the subsequent time frame.
 2. The computer memory of claim 1, furthercomprising computer instructions that cause the one or more computersto: when the first and second time slots of the time frame areunavailable: send the second message that is responsive to the firstmessage in a third time slot of the time frame, the third time slotbeing different from the first and second time slots in the time frame;and receive the third message that is responsive to the second messagein the third time slot of the subsequent time frame.
 3. The computermemory of claim 1, further comprising computer instructions that causethe one or more computers to: reserve the first time slot of thesubsequent time frame prior to receiving the third message when thefirst time slot of the time frame is available; and reserve the secondtime slot of the subsequent time frame prior to receiving the thirdmessage when the first time slot of the time frame is unavailable. 4.The computer memory of claim 1, further comprising computer instructionsthat cause the one or more computers to: reserve the first time slot ofthe subsequent time frame prior to receiving the third message when thefirst time slot of the time frame is available; unreserve the first timeslot after receiving the third message in the first time slot of thesubsequent time frame; reserve the second time slot of the subsequenttime frame prior to receiving the third message when the first time slotof the time frame is unavailable; and unreserve the second time slotafter receiving the third message in the second time slot of thesubsequent time frame.
 5. The computer memory of claim 1 wherein thefirst message comprises a Common Access channel (CAC) message and thesecond message comprises a Common Link Channel (CLC) message.
 6. Thecomputer memory of claim 1 wherein the first message comprises a channelaccess request for communication.
 7. The computer memory of claim 1wherein the first message comprises a channel access request forcommunication, the second message comprises a channel measurementrequest, and the third message comprises channel measurement data. 8.The computer memory of claim 1 wherein the first selected time slot isone of the predetermined number of available sequential time slots. 9.The computer memory of claim 8 wherein the first selected time slot isthe first sequential time slot.
 10. A computer memory having computerinstructions embedded thereon for dynamically assigning time slots inwireless communication system, the computer readable medium comprisinginstructions that cause one or more computers to: identify a nextavailable time slot time frame having plurality of time slots; reservethe identified time slot of the time frame; send a first message in thereserved time slot of the time frame; receive a second message that isresponsive to the first message in the corresponding reserved time slotof a following time frame; and unreserve the reserved time slot forsubsequent use.
 11. The computer memory of claim 10 wherein the firstand the second message comprise messages for call establishment.
 12. Amethod for dynamically assigning time slots between a base unit and atransceiver unit of a wireless communication system having apredetermined number of time slots per time frame, the methodcomprising: receiving a first message; processing the first message andgenerating a second message in response thereto; when a first selectedtime slot of a time frame is available: sending the second message thatis responsive to the first message in the first time slot; receiving athird message that is responsive to the second message in the first timeslot of a subsequent time frame; when the first time slot of the timeframe is unavailable: sending the second message that is responsive tothe first message in a second time slot of the time frame, the secondtime slot being different from the first time slot in the time frame;and receiving the third message that is responsive to the second messagein the second time slot of the subsequent time frame.
 13. The methodclaim 12, further comprising: when the first and second time slots ofthe time frame are unavailable: sending the second message that isresponsive to the first message in a third time slot of the time frame,the third time slot being different from the first and second time slotsin the time frame; and receiving the third message that is responsive tothe second message in the third time slot of the subsequent time frame.14. The method of claim 12, further comprising: reserving the first timeslot of the subsequent time frame prior to receiving the third messagewhen the first time slot of the time frame is available; and reservingthe second time slot of the subsequent time frame prior to receiving thethird message when the first time slot of the time frame is unavailable.15. The method of claim 12, further comprising: reserving the first timeslot of the subsequent time frame prior to receiving the third messagewhen the first time slot of the time frame is available; unreserving thefirst time slot after receiving the third message in the first time slotof the subsequent time frame; reserving the second time slot of thesubsequent time frame prior to receiving the third message when thefirst time slot of the time frame is unavailable; and unreserving thesecond time slot after receiving the third message in the second timeslot of the subsequent time frame.
 16. The method of claim 12 whereinthe first message comprises a Common Access channel (CAC) message andthe second message comprises a Common Link Channel (CLC) message. 17.The method of claim 12 wherein the first message comprises a channelaccess request for communication.
 18. The method of claim 12 wherein thefirst message comprises a channel access request for communication, thesecond message comprises a channel measurement request, and the thirdmessage comprises channel measurement data.
 19. The method of claim 12wherein the first selected time slot is one of the predetermined numberof available sequential time slots.
 20. The method of claim 19 whereinthe first selected time slot is the first sequential time slot.